The present invention relates to a method and an apparatus for molding and, in particular, relates to a method and an apparatus for molding a plurality of plastic characters on the surface of a card stock blank to thereby form a printing card or the like.
The common way in which printing token cards are presently made is by an embosing process. Typically, such cards are made from plastic base sheets and embossed with characters, such as letters and/or numbers. The embossing process results in raising the characters from the blank so that the characters on the card act as type when a printing roller or the like is passed over a card. The embossing process, of course, results in hollow characters being formed and pressure which is applied to the characters during printing causes repeated deflection and stressing thereof. As a result, the characters sometimes become deformed or distorted, and the cards sometimes lose their ability to produce quality printing.
In order to solve the above problems with the embossed credit cards, it has been suggested that molded plastic characters be formed on a blank. Such characters would not be hollow, but rather would be solid, and would not, therefore, be subject to the same degree of deformation and stressing as embossed characters.
Various techniques for molding the plastic characters on a blank to form a credit card have been suggested. Ballard et al. U.S. Pat. No. 3,553,787 is an example thereof. The known techniques have not been completely satisfactory and are subject to certain practical problems, the greatest of which is sprue detaching and surface smoothing. These problems center around the handling of the flowable plastic material which is to form the characters. Typically, the equipment for forming the characters includes a plurality of die wheels having die cavities therein and which are rotated in order to position a given cavity defining a selected character in position for molding. The manner in which the plastic material has been delivered to the die cavities is also a potential source of problems since the plastic material is passed through a passage defined by aligned openings in the die wheels which is subject to clogging and which tends to impair individual wheel operation during setting, and each individual cavity is provided with a gate which gives rise to a sprue when the character is unmolded.